This proposal aims to investigate the mechanism of the antimicrobial action of the human salivary mucin MUC7 derived peptide 20-mer in bacteria and its therapeutic potential. It aims to demonstrate that its mode of action is similar to the one in fungi, but different from that of a similar antimicrobial peptide, histatin-5. Investigation into the therapeutic potential of the 20-mer will involve experiments with periodontal pathogens. Experimental methods will include measure of transmembrane potential activity, microscopy to record images of the membrane after exposure to peptide and spectrophotometric analysis of location of peptide at the membrane through utilization of a distribution dependent flurophore. The influence of net positive charge on the potency of 20-mer will be investigated by cidal assays with chemically modified peptides and peptides with substituted amino acids. In addition, cells with varying surface charge will be compared for susceptibility to 20-mer. Dependence of metabolic activity will be assessed to differentiate the mode of action of 20-mer from that the structurally similar peptide histatin-5 and to demonstrate that mitochondria are not the targets of this peptide. Inhibition of periodontal enzymes will be tested to examine if antimicrobial activity extends beyond cidal activity and agglutination. Lastly, Western blotting will be utilized to demonstrate 20-mer could exist in saliva. This proposal aims to prove that 20-mer exerts activity in bacteria in a manner similar to its action in fungi with potency dependent on charge, independent of metabolism, and with an intracellular target. It will show that antimicrobial activity of 20-mer could be useful in the treatment of bacterial diseases like periodontal disease.